Method of making resin-fiber compositions



Patented Aug. 1939 METHOD oF MAKING RESlN-FKBER coMrosrrroNs Norman D. Hanson, Bloomfield, N. J., assignor to Bakelite Corporation, New York, poration of Delaware- N. Y., a cor- No Drawing. Application April 8, 1935,

' Serial No. 15,349

5 Claims.

The invention relates to resin-fiber compositions and to aprocess of producing the'same, and particularly/to a quick-curing composition comprising fibrous material and heat-harden- 5 able phenol-aldehyde condensation products of special value in molding articles under heat and pressure.

l A principal object of theinvention is theproduction of resin-fiber compositions which will be l quick-curing and sufiiciently free-flowing to fill the various type molds used in hotpressure molding. This and other advantages are obtained by the method of the invention which broadly comprises treating a mixture of a fibrous P material and a well-advanced phenol-aldehyde resin, advantageously in sheet form, with arreeflowing; quick-curing phenol-aldehyde resin. In this way; for example, quick-curing products of substantial resin content may be obtained with go the use of only a relatively small amount of highly reactive resin, yet equivalent in speed to the curing cycle of the more reactive resin and by the use of such low cost slowly reactiveresin in major portion of the bond, thereby decreasw ing the cost of manufacture and avoiding disadvantages arising in the melding of compositions containing large amounts of free-flowing highly reactive resinous materials The invention also makes it possible to mold articles of considerable thickness in a shorter period of time than has heretofore been thought possible, by providing a substantial portion of the resin content of the molding material in an already well-advanced stage of reaction and thus'greatly as reducing the disturbancescaused by vapors like water and ammonia given oil in the actual curing operation of the present commercial highly reactive and quick curing-type of resinoids.

In practicing the invention, a fibrous material so may be impregnated with a resin varnish or a liquid resin, or it may be admixed with the resin in dry powdered form or ina suspension or emulsion. The resin is either reacted to a. high state of advancement before mixing with the fibrous materials, or the mixtureof the fibrous material and resin is heated to cause the rain to be advanced to the gel point. Theflbrous material may be in sheet form before mixture with the resin, or the resin-fiber mixture maybe so formed into. sheetsafter it is made, for ex-v ample, by admixing wet fibrous pulp with an aqueous suspension-or emulsion of the resin in a paper mill beater or by mixing a dry pulp with a solution of the resin in a volatile solvent. The

as sheet, after drying, if necessary, is then coated or impregnated with a highly reactive resin and again dried, if desirable. The treated sheets may be formed into articles by heating under pressure, or the sheets may" be fused between hot rolls and then ground to forma molding P wder.

The following isan illustrative example of the invention:

A mixture of 100 parts tar'phenols, boiling above 212, parts of of high-boiling coal 37% formaldehyde solution, 3 /2 parts, of 28% ammonium hydroxide solution and 75 parts of asphalt was refluxed together until a very stiff,

slowly hardening tyne .mixture formed into resin was produced. This sheets, containing about 25% of resin and dried with heat, thus further advancing the resin. .The sheet so formed would not bond under a heat pressure cycle of C.

thickness built up out of these sheets molded in two minutes and discharged hot from the mold.

of delamination or bliste'ring. When the sheets were passed through hot rolls and ground to a powder they produced a molding powder which discharged hot from the mold in two minutes curing time without without showing signs evidence of blistering. Other phenols, such as resorcinol, meta-cresol or meta-xylenol, may be used in the production of the resins used in the invention. Resorcinol isof particular advantage in increasing the rate of cure of the highly reactive resin for the second resinouscomponent. v

Other aldehydes may be used in the place of formaldehyde, particularly in the production of the resin used as the first resinous component.

For example, the reaction products of phenol, cresol, xylenol and the like with furfural are suitable for this purpose.

Accelerating agents, methylene tetramine, modifying agents, may ti'ons of the invention.

such as lime or hexaor plasticizing or other added to the composiresinwasincorporated with krait pulp and them advanced resin and the free-flowing, quick-curingresin in the hot molding compositions of the invention may be varied within wide limits, de-

pending upon the specific resins, the fibrous material, the use to which the compositions are to be put, and other factors, it in general advantageous to use from 15% to 40% of the welladvanced resin and from 5% to 25% of the freeflowing quick-curing resin.

I claim:

1. A method of making a quick-curing resinfiber composition which comprises treating a sheeted mixture of a fibrous'material and from 15 to 40% of a phenol-aldehyde resin reacted approximately to the -'gel point with from 5 to 25% of a free-flowing, quick-curing phenolaldehyde resin.

2. A method of making a quick-curing resinfiber composition which comprises mixing 'from 15. to 40% of a. phenol-a1dehyde.resin reacted approximately .to thegel point with a fibrous material, forming the mixture into sheets and treating the sheeted mixture with from 5 to 25% resin.

2,170,755 While the relative proportions of the well- 3. A method of making a quick-curing resinfiber composition which comprises mixing from 15 to 40% of a slow-curing phenol-aldehyde resin reacted approximately to the gel point with a fibrous material, forming the mixture into sheets and treating the sheeted mixture with from 5 to 25% of a free-flowing, quick-curing phenolaldehyde resin. I

4. A method of making a quick-curing resinfiber composition which comprises mixing a fibrous material with from 15 to 40% of a phenolaldehyde resin, forming the mixture into sheets, reacting the resin approximately to the gel point, and treating the sheeted mixture with from 5 to 25% of a free-flowing, quick-curing phenolaldehyde resin.

5. A method of making a quick-curing resinfiber composition which comprises mixing a fibrous material with from 15 to 40% of a slowcuring phenol-aldehyde resin, forming'the mixture into sheets, reacting the resin approximately to the gel point, and treating the sheeted mixture with from 5 to 25% of a free-flowing, quick-curing phenol-aldehyde resin. 1

NORMAN D. HANSON. 

